Fuel feed device for aircraft



Oct. 27, 1942.

R. AVIGDOR FUEL FEED DEVICE FOR AIRCRAFT Original Filed Feb. 13, 1939Patented Oct. 27, 1942 UNITED FUEL-FEED DEVICE FOR AIRCRAFT RifatAvigdor, Toronto, Ontario, Canada Original application February 13,1939, Serial No.

256,157.- Divided and this application April 28, 1941, Serial No.390,817. In Germany September 2, 1938 9 Claims.

This application is a division of Patent No. 2,263,864, granted Nov. 25,1941, entitled Fuel feed device for aircraft.

The invention relates to an arrangement in fuel feeding devices foraircraft. The liquid fuel required for the operation of the internalcombustion engine of an aeroplane is fed to the engine by means of apump from one or more tanks arranged at suitable places in theaeroplane. This pump is preferably arranged as a so-called submersiblepump set within the fuel tank or tanks. The pump is driven by anelectro-motor, which in a suitable way is mounted in the casing of thepump. The arrangement is such that the pump is located in closeproximity to the tank bottom and is suspended from the upper cover plateof the tank.

The tank may have thick walls, which, if necessary, are either coveredby insulating material or consist of non metallic substances.

Now it has occurred in practice that tanks of this type behave asheat-accumulators so that the fuel within the tank is heated andaccumulates the heat absorbed for a considerable time. The heating is.during the summer months, a-consequence of the sun rays and the outsidetemperature. Now as soon as an aeroplane with a fuel heated in this wayascends to considerable height the fuel in the tank will begin toevaporate and gasify due to the decreasing air pressure. The ef feetthereof is that the pump can no longer satisfactorily feed the fuel tothe engine since generally a blade pump is used, the feeding action ofwhich will stop as soon as trapped gases or vapors of the fuel occur inthe feed path of the pump. A cooling of the fuel within the tank isimpossible by reason of the insulating effect of the walls, inparticular since the ascending of an aeroplane to considerable heighttakes place in a short time. The fuel supply is therefore uncertain andthe case may occur that the supply is entirely interrupted.

When the fuel within the tank is heated gases and vapors are trapped, inparticular closely above the bottom of the tank. Now, since the inlet ofthe feed pump is located at this place within the tank it may occur thatthe fuel supply is already stopped in the case of a small increase ofthe temperature of the fuel. Moreover, just at the inlet zone of thepump a somewhat reduced pressure is created by the suction of the pumprotor as compared with the pressure in the surrounding mass of liquid,whereby the evaporation or gasification of the fuel will occur stillearlier or more intensively.

These disadvantagesare removed, according to the invention, by effectinga cooling of the fuel by circulation from the tank through an outsidecooler and back to the tank. This circulation of the fuel may accordingto the invention, be' produced by means of a submersible pump in thetank. Preferably the return flow of the fuel from the cooler is to enterat or in the vicinity, of the inlet of the pump feeding the fuel to themotor.

Instead of a submersible pump maintaining the circulation for thecooling of the fuel, according to the invention use may also be made ofthe pump feeding the fuel to the engine. In this case, part of the fueldelivered by the engine feed pump is branched off and passed through acooler, located outside the tank. The, return flow of the fuelpreferably enters again at or in the vicinityof the inlet of the feedpump supplying the motor. I

The cooler is arranged at a convenient place on the aeroplane preferablyso as to be subjected to the air current. A cooler of this nature needhave but'relatively small dimensions since the outside temperature atconsiderable height is'very low and moreover the strong air currentcaused by the flight produces a vigorous cooling.

Since for devices of the type described above pumps are used whichalways have a feeding capacity which is greater than the fuelconsumption of the engine; the branching off of part of the fuel for thecirculation through a cooler for the cooling of the fuel contents of thetank may be carried out without taking any further steps.

The fuel returning from. the cooler is introduced into the inlet of,thefeed-pump at a certain pressure or at a certain speed so that thepump will have to produce less power than if the fuel were flowing tothe pump only at the pressure head of the fluid column in the tank. Theenergy used for the circulation of the fuel to cool the fuel istherefore partially compensated by the smaller amount of energy to beproduced by the pump. The cooling device'as such therefore consumesrelatively little power.

It is especially advantageous to construct in accordance with theinvention the outlet end of the return conduit so as to form an injectorfor to effectively cool in a short time the contents of a fuel tank bycirculation; so that in the hot test season and under verystrongradiation of the sun the temperature of the fuel is kept so lowthat no evaporation or gasiflcation can occur.

The invention is illustrated in the drawing schematically and by way ofexample.

Figure 1 is an elevation of an embodiment of the device according to theinvention.

Figure 2 is an'elevation, partly sectional, of the lower portionof thefeed-pump, and

Figure 3 is a view similar to Figure 2 illustrating a modification.

i denotes the tank of an aeroplane in which the submersible pump 2 issuspended. The fuel in the tank flows to the pump through the strainer 3constituting the lower end of the pump. The fuel is fed throughthe pipeconduit 4 to the internal combustion engine in the direction of thearrow 5. g

In the embodiment shown in Figure 1 another pump 6 is arranged in thetank I to which pump the fuel flows-through a strainer I mounted on thepump 6. The pump 8 feeds the fuel through a pipe conduit 8 into a coolerS. .The cooler is mounted on the aeroplane in such a manner that it issubjected to'the air current or is exposed in such a manner that thefuel is effectively cooled.

' flows at a certain speed or at a certain pressure outlet end ii ofsaidconduitis located within a tapering hollow member I! and togethertherewith forms' an injector. By the fuel leaving. the 4 outlet I [inthedirection of the arrow It the fuel surrounding the injector isdrawnand carried along in the direction of the arrows I9. At the same timethe fuel carried along by the action of the-injector is in this waycooled, while the pressure head of the return conduit at the 10 sametime'promotes the feed. Now, the fuel to the rotor I! of the feed pump,so that the advantages referred to above are obtained,

opens at H into the inlet strainer 3 of the feedpump 2 or into thevicinity thereof.

The operationof this embodiment is as followsz The pump 6 feeds fuelcontinuously through the conduit 8 into the cooler 9. In the cooler thewarm fuel coming from the tank is cooled and flows in this cooledcondition through the conduitv i0 back to the tank. Part of the fuelleaving the outlet endll of 'the conduit III is mixed with the warm fuelin the tank I and already thereby reduces gradually the temperature ofthe fuel. A further portion of the fuel leaving the outlet end II flowsdirectly into the inlet strainer 3 and is supplied to the engine throughthe conduit 4 by the main feed pump 2.

After a short time the total amount of fuel contained in the tank I haspassed through the cooler 9 whereby a rapid cooling of the fuelobtained. so that no evaporation or gasiiication due to the heataccumulating walls of the tank can occur.

Now in order to utilize the pressure head of I the circulating fuelresulting from the operation of the pump and the position of the cooler9, the outlet end of'the return conduit of the fuel is formed .as aninjector as shown in the embodiment according to Figure 2. The casing ofthe pump, through which the fuel is fed to the engine, is again denotedby 21.

the conduit 4 to the engine. Similarly as in the embodiment according toFigure 1 the conduit it of the ,retumflow of the cooler s entersunderneath the inlet of the feed pump. The conduit l0 is provided with aspecial heat insulating layer I 6, so that the fuel is supplied to thefeed. pump at the lowest possible. temperature. The 7 motor feed P mp wlh m fil from said The injector device is shown in Figure 2 onlyschematically. In the existing pumps provided with an" inlet strainer,it is preferred to use a plurality of injectors arranged in a circlearound the inlet strainer in the form of an injectorannulusm The cooler'9 is shown in thedrawing only schematically and acoil cooler or acooler of any other typ may be used for the same purpose.

I claim} a Y 1. A fuel feed device for aircraft comprising a fuel tank,-a cooler located outside the tank, a

submersible motor feed pump-unit in the tank for withdrawing fuel fromsaid tank, an additional submersible pump unit in the-tank forwithdrawing fuel-from said tank the feed con duit of which is connectedto the cooler and a return conduit from the cooler to the inlet of themotor feed pump unit to return the cooled fuel to said pump unit. 7

2 A fuel feed device for aircraft comprising a fuel tank, a coolerlocated outside the tank, a submersible motor feed pump unit in the tankfor withdrawing fuel from said tank, an additional submersible pump unitin the tank for withdrawing fuel from said tank the feed conduit ofwhichis connected to the cooler and a return conduit from the coolertothe vicinity of the inletof the motor feed pump unit to return thecooled fuel to said pump unit.

3. A fuel feed device for aircraft comprising a fuel tank, a coolerlocated outside the tank, a submersible motor feed pump unit in the tankfor withdrawing fuel from said tank, an additional submersible pump unitin the tank for withdrawlngfuel from said tank the feed conduit of whichis connected to the cooler and a a return conduit from the cooler to theinlet of the motor feed pump unit to return the cooled fuel to said pumpunit, the outlet end of said return conduit beingfformed as an injectoropen ing into the, fuel surroimding said outlet end.

4. .A-fuel feeding device for aircraft comprisinga fuel tank, a coolerlocated outside said tank, an engine feed pump in said tank forwithdrawing fuel from said tank, means independent ofsaid feed pump. forfeedingfuel from said tank to said cooler and vmeans for returning thefuel -.at;fl= w cooled by said cooler. to said tank of the inlet ofsaidpump.-

5. A'fuel mam; device for "eaeeamsam nrst'named pump.

6; A fuel feed device for aircraft comprising a fuel tank, a coolerlocated outside said tank, a

tank, a second pump for withdrawing fuel from said tank having itsdischarge conduit connected to said cooler and a return conduit fromsaid cooler to the inlet of said motor feed pump to feed the cooled fuelto said motor feed pump.

'7. A fuel feed device for aircraft comprising a fuel tank, a coolerlocated outside said tank, a motor feed pump for withdrawing fuel fromsaid tank, a second pump for withdrawing fuel from said tank having itsdischarge conduit connected to said cooler and a return conduit fromsaid cooler to the vicinity of the inlet of said motor feed pump to feedthe cooled fuel to said motor feed pump.

8. A fuel feed device for aircraft comprising a fuel tank, a coolerlocated outside said tank, a motor feed pump for withdrawing fuel fromsaid tank, a second pump for withdrawing fuel said tank having its feedconduit connected to said cooler and a return conduit from said coolerto the inlet of said motor feed pump to feed the cooled fuel to saidmotor feed pump, said return conduit terminating in annuiarly arrangedinjectors at the inlet of said fuel pump.

RIFAT AVIGDOR.

